<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>donghai</title>
</head>
<body>

    <p>请输出一个 5 到 10 之间的数字:</p>

    <input id="demo" type="text">
    <button type="button" onclick="myFunction()">测试输入</button>
    <p id="message"></p>

    <script>
        function myFunction() {
            var message, x;
            message = document.getElementById("message");
            message.innerHTML = "";
            x = document.getElementById("demo").value;
            try { 
                if(x == "")  throw "值为空";
                if(isNaN(x)) throw "不是数字";
                x = Number(x);
                if(x < 5)    throw "太小";
                if(x > 10)   throw "太大";
            }
            catch(err) {
                message.innerHTML = "错误: " + err;
            }
        }
    </script>

</body>
</html>